The present invention relates to processes and compositions for dyeing hydrophobic polymer fibers such as polyester, polyester blends, nylon, nylon blends and polyester/nylon blends.
The typical polyester dye is a disperse dye. Conventionally, polyester and polyester blend disperse dye carrier/levelers consist of a fiber swelling solvent and an emulsifier package. The emulsifier package, which contains one or more emulsifiers stabilizes the final carrier/leveler product and allows the solvent to be dispersed evenly in water.
Disperse dyeing processes are typically used to dye products (goods) including carpet, flatgoods, yarns and finished goods made at least in part of hydrophobic polymer filaments or fibers including polyester, nylon, polyacrylonitrile and polyurethane (E. R. Trotman (ed.) "Dyeing and Chemical Technology of Textile Fibers," Sixth Ed., Charles Griffin and Co. Ltd., High Wycomb, 1984).
The typical disperse dyeing systems used in the art include water-based processes. Water provides a medium in which to disperse the solvent and dye to facilitate contact of the dye with all areas of the goods being dyed in order to produce level dyeing of the goods. In addition, the water-based processes permit utilization of nearly all of the dye in the dyeing solution.
Typical disperse dyeing processes utilize a dyeing solution comprising a carrier/leveler composition (solvent and emulsifier), dyestuffs and water. The dyestuff dissolves in the solvent and the emulsifier disperses the solvent containing dissolved dyestuff into the water. The dye bath is then heated to temperature ranging from about 180.degree. F. to about 212.degree. F. The goods to be dyed are put in contact with the dye bath by various standard means.
Although not thoroughly understood, the general principle by which hydrophobic polymer fibers and filaments and various blends of those fibers are dyed is by the use of a carrier/leveler composition containing a solvent for the dyestuff that swells the polyester fiber, thus, opening the molecular pattern of the fiber to enlarge the interstitial spaces and allowing the dye to "move into" the fiber and dye the fiber. It has been known that solvents, such as aromatic and halogenated aliphatic hydrocarbons and phenols, accelerate the adsorption and absorption of disperse dyes into the fiber. Thus, the solvent portion of the dyeing solution is called a carrier.
Solvents in which the typically hydrophobic disperse dyes are soluble are not water soluble. Therefore, the carrier/leveler must include an emulsifier in order to avoid an oil/water type of interface which would cause spotty or unlevel dyeing. The emulsifier disperses the solvent portion of the carrier in water. This emulsifier generally consists of at least one chemical that contains both a hydrophobic and hydrophilic portion on the same molecule. The solvent containing the dissolved disperse dyes is attracted to the hydrophobic portion of the emulsifier (leveler) while the hydrophilic portion of the emulsifier distributes itself evenly in the water. The result is that the solvent and dyestuff are dispersed evenly in the dyeing solution and form a solvent film on the fiber, which causes level dye application. Thus, this disperse dyeing process is known as level dyeing and the composition which is used in the dyeing solution with the dyestuff and water is called a carrier/leveler.
Polyester dye carrier/leveler compositions for use in traditional disperse dyeing processes have usually had less than 2% water as a component. If more than 3% to 5% water is present, the final product is usually milky white and usually requires a special stabilizer to prevent stratification. An example of a traditional polyester dye carrier/leveler consists of 25% to 40% biphenyl, 5% to 25% emulsifier and 40% to 65% of a traditional, hazardous solvent. Traditional solvents include aromatic hydrocarbons and ethers: biphenyl, methylbiphenyl, diphenyl oxide, naphthalene, 1-methyl naphthalene, 2-methylnaphthalene, dimethylbenzene (xylene) and methylethylbenzene; halogenated aromatic hydrocarbons: monochlorotoluene, 0-dichlorobenzene and 1,3,5 trichlobenzene; halogenated aliphatic hydrocarbons: trichloroethylene and methylene chloride; aromatic esters: methyl benzoate, butyl benzoate and benzyl benzoate; phthalates: dimethyl phthalate, diethyl phthalate, diallyl phthalate and dimethyl terephthalate; and phenolits: orthophenyl-phenols and methylcresotinate.
Disperse dyeing processes are known for the dyeing of nylon fibers and filaments. The traditional nylon disperse dyeing process uses a leveling agent comprising a transester of a fatty acid, such as coconut fatty acid reacted with an ethoxylated nonylphenol. The transester molecule has both a hydrophobic (fatty acid) end and a hydrophilic (ethoxy) end. The hydrophobic end attracts the hydrophobic disperse dyestuff, while the hydrophilic end allows the leveling agent and dyestuff to disperse in the water of the dye bath. The hydrophobicity of the nylon fiber attracts the dyestuff which is brought in close contact to the surface of the fiber where it can then be absorbed into the fiber.
Processes for dyeing hydrophobic polymer fibers are known which do not disperse the solvent carrier and dye in water. These processes, known as "solvent dyeing" processes, have the disadvantages of requiring a higher concentration of solvent on the weight of the goods, compared to disperse dyeing processes, which makes the process more costly, in terms of solvent costs, solvent recovery costs and the costs of removing the solvent from the dyed material. In addition, the solvent dyeing processes are more dangerous to workers and to the environment.
It has long been known that many of the traditional solvents, used in disperse dyeing, are hazardous to the environment and the public health. Thus far, efforts to develop an effective substitute for traditional solvents that does not have the same environmental impact as traditional solvents have been unsuccessful.
Terpenes, such as the terpene hydrocarbon d-limonene, have been used as biodegradable scours for textiles produced from both synthetic and natural fibers as well as blends. Scouring is a process whereby contaminants, such as spinning oils, and natural oils on natural fibers, are removed from fibers before dyeing to facilitate adsorption and absorption of the dyestuff on the fiber. In disperse dyeing batch processes, scours are not generally used.